In the automotive market, DC to DC converters must operate through a wide input voltage range defined by a normal variation of the supplied input voltage as well as by some transient voltages. Such a transient voltage may be, for example, a cranking pulse, i.e., a huge voltage drop that can happen when certain events occur simultaneously, for example, a discharged battery, low temperatures, and the driver attempting to start the car.
A DC to DC converter may be used to compensate such a cranking pulse and may additionally provide an adapted voltage level to connected electronic devices. Such a DC to DC converter may transform an input voltage Vin to an output voltage Vout, wherein the output voltage Vout may be higher or lower than the input voltage Vin. A DC to DC converter capable of regulating an output voltage regardless of the input voltage Vin is called a buck-boost DC to DC converter. The buck-boost DC to DC converter comprises a buck converter that converts an input voltage Vin to a lower output voltage Vout and a boost converter that converts an input voltage Vin to a higher output voltage Vout. The buck-boost converter may be called non-inverting when the sign of the input voltage Vin is maintained.
The buck-boost DC to DC converter has too provide a constant output voltage Vout. Therefore, a transition between an operation of the buck converter (buck mode) and an operation of the boost converter (boost mode) is necessary when the input voltage Vin drops from a starting value that is higher than the desired output voltage Vout to a final value that is lower than the desired output voltage level Vout. This transition from buck mode to boost mode and vice versa must be managed smoothly and efficiently.